1. Field of the Invention
The invention relates in general to transportation apparatus, and more specifically to passenger conveyors such as escalators and movable walks having a plurality of steps, platforms or pallets which are attached to a flexible conveyor formed of step links and step axles.
2. Description of the Prior Art
U.S. Pat. Nos. 3,677,388; 3,682,289 and 3,707,220, all assigned to the same assignee as the present application, disclose new and improved passenger conveyor apparatus, such as escalators, in which the steps are pulled up the incline by a toothed step link. A modular drive unit located in the truss, between the load bearing and return runs, just below the transition between the inclined portion and the upper horizontal portion of the escalator, includes a drive chain which engages toothed step links on both the upper load bearing run and the lower return run.
The escalator construction disclosed by the hereinbefore mentioned patents includes an endless belt having two sides, each of which are formed by pivotally interconnected, toothed step links. The step links are formed of a plurality of superposed, flat steel laminations. Step axles interconnect the two sides of the endless belt, and the steps are clamped to the step axles. The endless belt and steps are guided through the load bearing and return runs, as well as through the turnarounds which interconnect the load bearing and return runs, by axle rollers or guide wheels on the ends of the step axles, trailer wheels on the steps, and separate guide tracks for supporting the guide wheels and the trailer wheels.
The escalator construction of the hereinbefore mentioned patents provides many advantages over escalators which utilize a step chain and a top sprocket-drive machine to pull the steps up the incline. One of the most significant advantages is the substantial reduction in load on the working parts. As the length of the rise increases, the load on the parts remains low, with additional modular drives being added to the incline, as required. The rigid step links maintain a constant distance between the step axles, eliminating the need for tensioning devices, which are required with the step chain construction.
While the load on the conveyor parts of the modular drive escalator is low compared with the conventional drive, any reduction in the weight of the conveyor which can be achieved without sacrificing mechanical strength, would be desirable. A reduction in weight is usually accompanied by a reduction in part cost, and it reduces the dead load on the drive chain of the modular drive unit and on the track system, providing longer chain life and improved ride quality.